Introduction Good evening! I d like to thank Craig Freerksen for organizing this debate. I d also like to thank Dr. Turek for agreeing to participate. Finally, I d like to thank all veterans, including my opponent, for defending the right to have a debate like this. Now, speaking of our country, I thought I d borrow a slogan from the presidential campaign. I m not selling any hats, but I m here to make atheism great again. Definitions In this debate, we ve been asked to assess what best explains reality: naturalism or theism? Before we can answer that question, we need to have some idea of what we re talking about, so let me begin by defining some terms. First, by naturalism, I mean the view that the physical exists and, if the mental exists, the physical explains why the mental exists. 1 If naturalism is true, then there are no purely mental beings which can exist apart from a physical body and so there is no God or any person or being much like God. Second, by supernaturalism, I mean the view that the mental exists and, if the physical exists, the mental explains why anything physical exists. 2 If supernaturalism is true, then there is no purely physical matter which can exist without some sort of ultimate mental creator. Third, personal supernaturalism is a type of supernaturalism; it adds on the claims that one or more personal mental entities exist and, if a physical world exists, it or they produced the physical world for a purpose. 3 Fourth, theism is a type of personal supernaturalism; it adds on the claim that there is just one mental entity, God, who is all-powerful, all-knowing, and morally perfect. 4 Finally, fifth, otherism is a catch-all category. It says that both naturalism and supernaturalism are false. 5 Now the question before us in tonight s debate is this. What best explains reality: theism or naturalism? In support of a naturalistic answer to that question, I m going to defend three basic contentions: (1) The best explanation is the explanation with the overall greatest balance of intrinsic probability and accuracy; (2) Naturalism is an intrinsically more probable explanation than theism; and (3) Naturalism is a more accurate explanation than theism. 1 I owe this definition to Paul Draper. 2 I owe this definition to Paul Draper. 3 This definition is similar to, but not identical with, one offered by Paul Draper. 4 I owe this definition to Paul Draper. 5 I owe this definition to Paul Draper.
2 First Contention Let s look, then, at my first basic contention: the best explanation is the explanation with the overall greatest balance of intrinsic probability and accuracy. By intrinsic probability of a hypothesis, I mean the probability independent of the evidence we have for or against it. The intrinsic probability of a hypothesis is determined entirely by its modesty and coherence. 6 By accuracy of a hypothesis, I mean the degree to which a hypothesis s predictions correspond to reality. We measure accuracy by looking at evidence. By evidence I mean something which makes something else more probable than it would have been otherwise. Let me give you an example. 7 Imagine you have two jars of red and blue jellybeans. In the first jar, 90% of the jellybeans are blue and the rest are red. In the second jar, 90% of the jellybeans are red and the rest are blue. Now imagine you are handed a jelly bean from one of the jars, but you don t know which jar it came from. If it s a blue bean, that s evidence it came from the first jar, not the second. The blue bean doesn t disprove that it came from the second jar because the second jar also has blue beans, but it s more likely that it came from the first because there are more blue jellybeans in the first than in the second. Similarly, if it s a red bean, that s evidence it came from the second jar. The red bean doesn t disprove that it came from from the first jar because the first jar also has red beans, but it s more likely that it came from the second because it has many more red beans. Mathematicians have a formula called Bayes Theorem, which can be used to specify the relationship between intrinsic probability, accuracy, and the overall or final probability of a hypothesis. It follows from Bayes Theorem that a hypothesis is probably true, just in case it has a greater overall balance of intrinsic probability and explanatory power than do its alternatives collectively. Second Contention Let s look, then, at my second basic contention: naturalism is an intrinsically more probable explanation than theism. Intrinsic probability is determined by modesty, coherence, and nothing else. By modesty, I mean a measure of how much the hypothesis asserts. 8 The more a hypothesis claims, the more ways there are for it to be false and so, before we start looking at evidence, the less likely it is to be true. 6 I owe this to Paul Draper. 7 I owe this jelly bean analogy to Paul Draper. Draper s full analogy also includes an equal number of yellow jelly beans in both jars, where yellow signifies something that is equally likely to have come from either jar and hence is not evidence that it came from either jar. I have omitted the yellow jelly beans solely in the interest of time. 8 I owe this definition to Paul Draper.
3 By coherence, I mean a measure of how well the parts of a hypothesis fit together. 9 If the different parts count against each other, the hypothesis is less coherent and less likely to be true. Now consider naturalism and supernaturalism. They are symmetrical claims: naturalism claims that the physical explains the mental, while supernaturalism claims that the mental explains the physical. Both claims are equally modest and equally coherent. Before examining the evidence, both positions are equally likely to be true. 10 With these definitions in mind, then, I can now defend my second contention. Theism is a type of supernaturalism but could be false even if supernaturalism is true. Furthermore, theism is less modest than either supernaturalism or naturalism. Therefore, before we look at evidence, it is less likely to be true than supernaturalism or naturalism. 11 But that entails that naturalism is intrinsically more probable than theism. Third Contention Finally, let s move onto my third contention: naturalism is a more accurate explanation than theism for many facts. I d like to present seven lines of evidence that are red jellybeans, i.e., things more probable on naturalism than on theism. 12 Physical Matter (1) Naturalism is the best explanation for the fact that physical reality exists. 13 If naturalism is true, then physical reality must exist. That s just part of what naturalism means. If theism is true, however, things look quite different. The existence of physical reality doesn t disprove theism; if God exists, God could have created physical space, matter, and energy as part of a plan to create a universe for human beings. But God could have also chosen to create other minds without physical bodies, such as angels. Or God could have chosen to create nothing at all. In other words, God s existence doesn t require a physical reality. 9 I owe this definition to Paul Draper. 10 Paul Draper, God and the Burden of Proof, Secular Outpost (July 21, 2014), http://www.patheos.com/blogs/secularoutpost/2014/07/21/new-by-paul-draper-god-and-the-burden-ofproof/ 11 Paul Draper, More Pain and Pleasure: A Reply to Otte in Christian Faith and the Problem of Evil (ed. Peter van Inwagen, Eerdmans, 2004), 41-54 at 49. 12 Let N stand for naturalism, T for theism, and F for any of these facts. Using the symbol Pr(F H) to stand for the epistemic probability that F is true conditional upon H, then the claim that some fact is evidence favoring naturalism over theism should be understood as the claim that Pr(F N) > Pr(F T). 13 Jeffery Jay Lowder, Potential Objections to Swinburne s Cosmological Argument, The Secular Outpost (March 17, 2014), http://www.patheos.com/blogs/secularoutpost/2014/03/17/potential-objections-toswinburnes-cosmological-argument/. Note that here I am using the word matter as a way to provide a concrete example of something physical.
4 So because the physical has to exist on naturalism but does not have to exist on theism, it follows that the existence of physical reality is evidence favoring naturalism over theism. Success of Science (2) Naturalism is the best explanation for the fact that science has been so successful without the supernatural. 14 Imagine a library that contains textbooks for all of the sciences such as physics, chemistry, and biology and summarizes current scientific knowledge. The percentage of such knowledge which makes no appeal to the supernatural is extremely high. Of course, one hears about specific scientific questions which (allegedly) do not have a plausible naturalistic explanation, such as cosmological fine-tuning, the origin of life, and consciousness. But, even if that is or were true, the history of science contains numerous examples of naturalistic explanations replacing supernatural ones and no examples of the reverse. Indeed, naturalistic explanations have been so successful that even most theists concede that supernatural explanations are, in general, unlikely to be true. Such explanatory success is just what we would expect on naturalism which entails that all supernatural explanations are false than it is on theism. 15 And that s my second line of evidence against theism. Biological Evolution (3) Naturalism is the best explanation for the fact that complex life evolved from simple life. 16 I m going to list five scientific facts which support biological evolution. Since Dr. Turek likes acronyms, I m going to give you the evidence in an acronym, BONES. B is for biogeography; O is for vestigial organs; N is for natural selection; E is for embryology; and S is for stratified fossil record. 14 See Keith M. Parsons, Science, Confirmation, and the Theistic Hypothesis (Ph.D. Dissertation, Kingston, Ontario, Canada: Queen s University, 1986), 46; Paul Draper, Evolution and the Problem of Evil in Philosophy of Religion: An Anthology (3rd ed., ed. Louis Pojman, Wadsworth, 1997), 223-24; and idem, God, Science, and Naturalism Oxford Handbook of Philosophy of Religion (ed. William Wainwright, Oxford: Oxford University Press, 2004), 272-303; and Barbara Forrest, Methodological Naturalism and Philosophical Naturalism: Clarifying the Connection Philo 3 (2000): 7-29. 15 Draper 2004. 16 See Paul Draper, "Evolution and the Problem of Evil" in Philosophy of Religion: An Anthology (3rd ed., ed. Louis Pojman, Wadsworth, 1997), 219-230; cf. Louis P. Pojman, Philosophy of Religion (Mayfield, 2001), chapter 6.
5 Let s look very briefly at each of these. Biogeography First, the evidence indicates that the habitats of plants and animals are distributed in a puzzling way. For example, why are there no land-based mammals on any island more than 300 miles away from the mainland? As University of Chicago biologist Jerry Coyne puts it, The biogeographic evidence for evolution is now so powerful that I have never seen a creationist book, article, or lecture that has tried to refute it. 17 Vestigial Organs Secondly, a variety of animals have organs which display traits that would be unnecessary if the organs had been designed from scratch, but would have been useful to an ancestor. Natural Selection Thirdly, when the genetic differences between living things provides an advantage, things with that advantage tend to be more successful at survival and reproduction than things without that advantage. This is the essence of the process Darwin called natural selection. Embryology Fourthly, as Coyne points out, the evidence indicates that all vertebrate embryos begin development in the same way, looking like embryonic fish, but as they progress, they often go through strange contortions before reaching their final form. 18 Stratified Fossil Record Fifthly, the available fossil evidence indicates that as one goes from the oldest to the youngest layers of the fossil record, the layers show gradual change from simple to more complex life forms. Taken together, the BONES evidence is much more probable on biological evolution (which says that complex life evolved from simple life through trans-generational genetic change) 19 than it is on special creationism (which says that God created all life virtually simultaneously). 20 If either naturalism or supernaturalism is true, life could exist or not exist. If naturalism is true and life exists, evolution pretty much has to be true. But if theism is true, God didn t have to use evolution. Furthermore, since theism says that at least one mind existed before any physical matter, it gives a reason to expect that any other minds are 17 Jerry Coyne, Why Evolution is True (New York: Penguin, 2009), 88. 18 Coyne 2009, 56. 19 Draper 1997, 221. 20 I m using virtually simultaneously as a shorthand way of accounting for the seven literal days described in Genesis 1, in order to contrast that chronology with the sort of geological timescales needed for evolution.
6 fundamentally nonphysical. But that, in turn, leads us to predict conscious life was created independently of nonconscious life, contrary to what evolution claims. 21 So theism predicts that evolution is false. Thus, the scientific fact of evolution is more likely on naturalism than on theism, and so that s my third line of evidence against theism. Pain and Pleasure (4) Naturalism is the best explanation for the biological role (and moral randomness) of pain and pleasure. 22 I m going to give three lines of evidence. Moral Agents Experiencing Biologically Useful Pain and Pleasure First, moral agents experiencing biologically useful pain and pleasure. Suppose you are a teenager sleeping in a hotel that has caught on fire. The hotel is old and doesn t have smoke alarms. The fire gets closer and closer to you until you are actually in pain from the smoke and the intense heat. Your pain wakes you up in time for you to escape; you survive and start a family in your twenties. Your pain in this case was biologically useful because it contributed to your survival. This is just what we would expect on naturalism (and human beings are the products of evolution by natural selection). Sentient Beings Experiencing Biologically Useful Pain and Pleasure Second, moral patients experiencing biologically useful pain and pleasure. Most human beings are moral agents, people who can be held responsible for their actions and their consequences. But some human beings, such as young children and humans with certain mental disabilities, as well as non-human sentient animals, such as primates and dolphins, are moral patients: sentient beings who can be harmed from their own point of view, but are not responsible for their actions. On naturalism, we would expect that (biological) sentient beings, including moral patients, would experience pain and pleasure because moral patients are biologically similar to moral agents. On theism, however, we would predict that moral patients do not suffer the same kind of pain as moral agents because such pain plays no known moral role in the lives of the moral patients who experience it. Sentient Beings Experiencing Pain and Pleasure Not Known to be Useful Third, sentient beings experiencing gratuitous pain and pleasure. Consider, for example, an animal trapped in a forest fire, suffering horrific pain as it slowly burned to death. On the one hand, this kind of pain is biologically appropriate: it 21 Draper 1997, 224. 22 Paul Draper, Pain and Pleasure: An Evidential Problem for Theists. Nous 23 (June, 1989), 331-350.
7 is biologically useful that animals in general feel pain when they come in contact with fire. But, on the other hand, this specific instance of pain was not biologically useful because it did not contribute to the biological goals of survival or reproduction. On naturalism, this is just what we would expect. If naturalism is true, all animals are the byproducts of unguided evolution by natural selection, which is both indifferent to suffering and incapable of preventing it. But if theism is true, God could "fine tune" animals so that they only experience physical pain and pleasure when it was morally necessary. So theism leads us to expect that pain and pleasure are fundamentally moral phenomena, which just happens to be connected to the biological goals of survival and reproduction. That s a huge coincidence that naturalism doesn t need. So this evidence is very much more probable on naturalism than on theism. Mind-Brain Dependence (5) Naturalism is the best explanation for the fact that human minds are dependent upon the physical brain. 23 Philosopher Paul Draper of Purdue University puts it this way: "Consciousness and personality are highly dependent on the brain. Nothing mental happens without something physical happening." 24 Now Michael Tooley, a philosopher at the University of Colorado at Boulder, has stated five lines of evidence in support of this claim. 25 (1) When an individual's brain is directly stimulated and put into a certain physical state, this causes the person to have a corresponding experience. (2) Certain injuries to the brain make it impossible for a person to have any mental states at all. (3) Other injuries to the brain destroy various mental capacities. Which capacity is destroyed is tied directly to the particular region of the brain that was damaged. (4) When we examine the mental capacities of animals, they become more complex as their brains become more complex. (5) Within any given species, the development of mental capacities is correlated with the development of neurons in the brain. Take together, this evidence is much more probable on physicalism, which says that the mind is made only of physical matter, than it is on dualism, which says says that the 23 Jeffery Jay Lowder, The Evidential Argument from Physical Minds, The Secular Outpost (http://www.patheos.com/blogs/secularoutpost/2012/06/13/the-evidential-argument-from-physicalminds-apm/), June 13, 2012. 24 Paul Draper, "Opening Statement" in William Lane Craig and Paul Draper, Does God Exist? (videotape, West Point, NY, 1996). 25 Michael Tooley, "Dr. Tooley's Opening Arguments" in William Lane Craig and Michael Tooley, The Craig-Tooley Debate: Does God Exist? (http://www.leaderu.com/offices/billcraig/docs/craigtooley2.html), 1994, spotted 25 Jan 99.
8 mind is made of two substances (the physical and the mental). if God exists, God is not in any sense dependent on physical arrangements of matter. So theism entails the existence of at least one unembodied mind. Furthermore, if God wanted to create other minds, he didn t need them dependent on physical brains. So the dependence of human minds on brains is evidence against the existence of any being who is supposed to have an unembodied mind, including God. Therefore, the physical nature of minds is evidence favoring naturalism over theism. Empathy and Apathy (6) Naturalism is the best explanation for the neurological basis of empathy and apathy, including some moral handicaps. 26 In many cases, our ability to choose do morally good actions depends upon our having properly functioning emotional capacities, especially empathy, i.e., our ability to identify what someone else is thinking or feeling and to respond to their thoughts and feelings with an appropriate emotion. 27 We now know, thanks to the relatively new discipline of neuroscience, that certain brain abnormalities cause people to experience less or even no empathy. 28 According to Simon Baron-Cohen of Cambridge University, There is a consensus in neuroscience that at least ten interconnected brain regions are involved in empathy. 29 These regions are shown on the slide. For example, violent psychopaths may know in some abstract sense that their behavior is morally wrong, but utterly lack empathy. 30 While theism is compatible with a neurological basis for moral handicaps, the fact that at least some moral handicaps can be explained neurologically is much more probable on naturalism than on theism. If theism is true, then that means both and (a) God creates some human beings with moral handicaps that are not the result of the freely chosen actions of any human being; 26 Jeffery Jay Lowder, The Evidential Argument from Physical Minds, The Secular Outpost (http://www.patheos.com/blogs/secularoutpost/2012/06/13/the-evidential-argument-from-physicalminds-apm/), June 13, 2012. 27 Simon Baron-Cohen, The Science of Evil: On Empathy and the Origins of Cruelty (New York: Basic Books, 2012), 16. 28 Baron-Cohen 2012, 39. 29 Baron-Cohen 2012, 28. 30 As Baron-Cohen points out, the neurological basis for moral handicaps challenges traditional views about moral responsibility. If zero degrees of empathy is really a form of neurological disability, to what extent can such an individual who commits a crime be held responsible for what they have done? This gets tangled up with the free will debate, for if zero degrees of empathy leaves an individual to some extent blind to the impact of their actions on others feelings, then surely they deserve our sympathy rather than punishment. See Baron-Cohen 2012, 160.
9 (b) These moral handicaps make it more likely that they will harm others. What moral justification would God have for allowing both (a) and (b) to obtain? This seems utterly surprising and completely random from a theistic, moral point of view, but precisely what we would expect on naturalism (and blind nature is indifferent to the moral consequences of brain abnormalities). 31 Nonresistant Nonbelief (7) Naturalism is the best explanation for nonresistant nonbelief (in God). 32 Imagine you re growing up in an orphanage and I told you I had met a man who claims to be your father and who really wants a relationship with you. Days, weeks, even months go by but you never actually meet your father. You never get a card, letter, phone call. In fact, the only evidence that your father is alive is my claim that he exists. Why haven't you heard from him? Perhaps your father is ashamed for abandoning you. Or maybe he s a prisoner of war and his captors won t even let him write you. Although you hope your father is alive and wants to meet you, you remain skeptical. Just as you do not believe your father is alive and wants to meet you, there are people who do not believe that God exists. 33 But notice that, whatever reasons we might invent to explain your earthly father s absence do not explain their heavenly father s absence. At least some of the people who deny God s existence are nonresistant nonbelievers. As philosopher John Schellenberg explains, their nonbelief is not in any way the result of their own emotional or behavioral opposition towards God or relationship with God or any of the apparent implications of such a relationship. 34 Such nonbelievers are open to having a relationship with God in fact, they may even want it but are unable to have such a relationship. But why, if God exists, does that happen? On naturalism, blind nature doesn t care whether anyone believes in God and so the fact of nonresistant nonbelievers is hardly surprising. On theism, however, this fact is very surprising. On theism, we would expect a perfectly loving God to always make a meaningful relationship available to those He loves. 31 Some theists have pointed out that moral evil, such as fallen angels or demons choosing to do evil, might explain so-called natural evils. This argument makes the inverse point: certain natural evils explain at least some moral evil. 32 J.L. Schellenberg, Divine Hiddenness and Human Reason (Ithaca: Cornell University Press, 1993); idem, 2007. 33 This sentence, of course, assumes that at least some (if not most) professions of atheism are genuine. Those familiar with intra-christian debates on apologetic methodologies will notice that I have just ruled out the claim of some (or all?) presuppositionalists, namely, that there are no atheists and instead there are only professed atheists. I agree with John Schellenberg: it would take something like willful blindness to fail to affirm that not all nonbelief is the product of willful blindness (even if some of it is). See J.L. Schellenberg, What Divine Hiddenness Reveals, or How Weak Theistic Evidence is Strong Atheistic Proof God or Blind Nature? Philosophers Debate the Evidence (http://infidels.org/library/modern/john_schellenberg/hidden.html), 2008. 34 Schellenberg 2008.
10 Conclusion So, in sum, we've seen seven lines of evidence that naturalism is true. I also happen to think there is some evidence for theism, but that it is outweighed by the evidence for naturalism. 35 In my other speeches, I will explain why I think this as I respond to Dr. Turek s arguments. 36 35 It follows from a Bayesian approach to evidence sketched in my first contention that there can be true evidence for a false proposition. Consider, for example, people convicted on the basis of eyewitness testimony for crimes they didn't commit, only to be exonerated years or decades later by DNA evidence. The eyewitness testimony was some evidence for a false proposition ("The defendant is guilty"), but it was greatly outweighed by the DNA evidence against that false proposition. The fact that there can be true evidence for false propositions should serve as a "warning flag" to anyone who wants to claim that there is absolutely no evidence for naturalism (or theism). There is no evidence for naturalism (or theism) does not follow from Naturalism (or theism) is false or even I believe naturalism (or theism) is false. 36 I am grateful to Paul Draper, John Danaher, Robert Greg Cavin, and Eddie Tabash, for helpful comments on a previous version of this speech.